1. Field of the Invention
The present invention relates to a method of and an apparatus for manufacturing self-developed instant photographic film units.
2. Description of the Related Art
The recent widespread use of instant photographic cameras has resulted in the mass-production of self-developed instant photographic film units. An instant photographic film unit comprises a mask sheet having a central image frame that determines a screen size, a photosensitive sheet comprising a transparent or opaque support layer covered with a photosensitive layer, a transparent sheet for spreading a developing liquid between itself and the photosensitive sheet, and a pair of rails or spacers for defining a gap for passage of the developing liquid therethrough between the photosensitive sheet and the transparent sheet. To the mask sheet, there are bonded a developing liquid pod or container for containing the developing liquid therein and a trap for holding an excessive developing liquid, on respective marginal edges on both sides of the image frame.
There are available instant photographic film units of various structures. For example, one instant photographic film unit includes a photosensitive sheet joined to the upper surface of a mask sheet, a transparent sheet joined to the upper surface of the photosensitive sheet by rails, and a developing liquid pod and a trap that are wrapped by marginal edges of the mask sheet which are folded over the transparent sheet perpendicularly to the rails. Another instant photographic film unit includes a photosensitive sheet and a transparent sheet that are successively stacked in a given order on a mask sheet, rails bonded to the photographic sheet and the transparent sheet, and a developing liquid pod and a trap that are bonded to the mask sheet perpendicularly to the rails.
Various processes have been proposed to manufacture instant photographic film units. One proposed process is disclosed in Japanese patent publication No. 62-55772, for example. According to the disclosed process, as shown in FIG. 141, sheets 1, 2, one of which is a photosensitive sheet and the other of which is a transparent sheet, are joined to each other by a joining station 3, and thereafter rails 5 that have been severed from a rail web 4 are heat-sealed across the sheet 1 to the sheet 2 which is wider than the sheet 1.
The joined sheets 1, 2 are cut off along central lines of the rails 5 by a cutter 6, and then bonded to a mask sheet 8 by a heat sealer 7. In a periphery bonding station 9, the entire edges of the sheet 2 are bonded to the mask sheet 8 in surrounding relation to an image area opening thereof. In an attaching station 10, a developing liquid pod 11 and a trap 12 are bonded to the mask sheet 8 on its opposite sides. Thereafter, in a folding station 13, the developing liquid pod 11 and the trap 12 are folded over the opposite edges of the mask sheet 8. After the assembly is sealed in a sealing station 14, the mask sheet 8 is cut off in a cutting station 15, thereby completing an instant photographic film unit.
In the folding station 13, the instant photographic film unit has its outer longitudinal dimensions determined when the developing liquid pod 11 and the trap 12 are folded over the opposite edges of the mask sheet 8. Though it is necessary to establish folding positions of the mask sheet 8 with high accuracy, such a requirement cannot sufficiently be met by the conventional process.
Another problem of the conventional process is that when the image area opening is formed in the mask sheet 8, difficulty arises in processing the scrap punched out of the mask sheet 8. Specifically, the scrap punched out of the mask sheet 8 needs to be processed reliably without fail because the mask sheet 8 itself is easily electrically chargeable, and the scrap tends to be attracted to the mask sheet 8 or another member due to electrostatic charges of the mask sheet 8.
Instant photographic film units should preferably be beveled at their four corners in order to avoid their being caught by other members and stacked in error. The conventional process is unable to bevel the corners of instant photographic film units efficiently because it requires a separate beveling step.
According to the conventional process, the developing liquid pod 11 and the trap 12 are supplied one by one to the opposite sides of the mask sheet 8, and then bonded thereto by a heat-sealing process. Therefore, the bonding of the developing liquid pod 11 and the trap 12 is so time-consuming that the overall process of manufacturing instant photographic film units remains inefficient.
According to the conventional process, the bonding of the sheets 1, 2 and the bonding of the entire edges of the sheet 2 in surrounding relation to the image area opening of the mask sheet 8 are also time-consuming. Since the times required by the other steps are determined depending on the times of these bonding steps, the other steps necessarily require an unwanted dead time, with the result that the overall process of manufacturing instant photographic film units cannot be made efficient.
Furthermore, according to the conventional process, the sheets 1, 2 and the mask sheet 8 are exposed to temperature and humidity changes caused by the heat-sealing steps. The photosensitive sheet, in particular, tends to shrink in the manufacturing process because it is susceptible to humidity. If the sheets 1, 2 shrink, then the mask sheet 8 to which the sheets 1, 2 are bonded is displaced in the direction in which it is fed, making it difficult for the developing liquid pod 11 and the trap 12 to be bonded in accurate positions with respect to the opening in the mask sheet 8, and resulting in a shift of the position in which each instant photographic film unit is cut off. Consequently, high-quality instant photographic film units cannot efficiently be manufactured.
The conventional process is carried out by a facility which is placed in a dark chamber, and hence the sheets 1, 2, the rail web 4, and the mask sheet 8 are attached and processed in the dark chamber. For this reason, the manufacturing steps of the conventional process are tedious and time-consuming, and hence the overall process cannot be made efficient.
Furthermore, the distance from the joining station 3 to the cutting station 15 is considerably long, and many components including the rails 5, the mask sheet 8, and the developing liquid pod 11 and the trap 12 are bonded in positions between the joining station 3 and the cutting station 15. Since the relative positions of the components are liable to vary along the long production line, it is highly difficult to keep each instant photographic film unit finally severed in the cutting station 15 at a constant quality level.
The sheets 1, 2 and the mask sheet 8 are unreeled from respective rolls of sheet. When the rolls are used up, the trailing ends of the sheets 1, 2 and the mask sheet 8 are spliced to the leading ends of new sheets 1, 2 and a new mask sheet 8, which then start being supplied to the production line. Thus, some instant photographic film units necessarily contain spliced joints of the sheets 1, 2 and the mask sheet 8 as defects. If the positions of those spliced joints are varied for some reason, then instant photographic film units with such defects cannot be identified.
According to the conventional process, after instant photographic film units have successively been manufactured, the worker places a certain number of instant photographic film units in a case. In order to prevent the instant photographic films from being exposed to extraneous light, the packaging process needs to be performed in a dark chamber. Therefore, the packaging process is tedious and time-consuming.
Inasmuch as each instant photographic film has the developing liquid pod 11 and the trap 12 positioned at opposite ends thereof, it is difficult to stack such instant photographic films one on another stably. Consequently, it is a complex task to stack and handle a certain number of, e.g., 10, instant photographic films in the dark chamber.
Therefore, the process of packaging manufactured instant photographic films to produce packaged products is considerably tedious and time-consuming and cannot be made efficient.